This invention relates to an apparatus for providing an optical indication of the pressure condition of a pressurized member. More particularly, in its preferred form, this invention relates to a device which will provide a light when the pressurized member is at a tolerable pressure and no light when the pressure falls below a predetermined value. The absence of light can then be used to activate electronic circuitry to provide an alert of the low pressure condition.
It is often important to know the internal pressure of a pressurized member and particularly to insure that the pressure does not fall below tolerance levels. A typical example is the pneumatic tire where the undetected low pressure condition is not only a hazard to the safe operation of the vehicle but also can be detrimental to the tire itself.
Many types of devices have been detected for monitoring the pressure condition of an inflatable member such as a tire. Some, like a permanently mounted pressure gauge, merely give a contant reading of pressure requiring one to periodically observe the status of the pressure. In other systems a low pressure condition actuates a transmitter with the receiver in the vehicle sounding to alert the operator of the vehicle of the low pressure condition. Similarly, ultrasonic devices have been employed to indicate a low pressure condition. But both the transmitter-receiver system and the ultrasonic system are subject to system failure and/or spurious activation and have therefore been considered inadequate.
At times a light source has been used to indicate a pressure problem. For example, each tire of a vehicle has been equipped with a battery to operate a light source which was activated when a low pressure condition existed. Such a system required a battery at each wheel or else the use of slip rings to connect the rotating light source to the battery of the vehicle. The light was used with electronic circuitry to warn the vehicle operator of a problem but because it was only operable under low pressure conditions, the operator of the vehicle had no way to test the optical system to assure himself that it was working properly.